Indoor photovoltaic cell with simple sandwich structure and preparation method thereof

Abstract

The invention discloses an indoor photovoltaic cell with a simple sandwich structure and a preparation method of the indoor photovoltaic cell, direct induction preparation of a high-quality antimony sulfide thin film on a conductive substrate is realized through a crystal nucleus engineering strategy, and the indoor photovoltaic cell with the device structure of an FTO conductive substrate / an antimony sulfide absorption layer / a metal electrode from bottom to top is obtained. Compared with a traditional conductive substrate / electron transport layer / antimony sulfide absorption layer / hole transport layer / metal electrode device structure, the photovoltaic cell has the advantages that the cell device structure is remarkably simplified, the device preparation period is greatly shortened, the preparation process is suitable for large-scale industrial production, the indoor photovoltaic efficiency of the obtained device is up to 6.12%, and the device is suitable for large-scale industrial production. Wide application prospects are shown in the indoor photovoltaic field.

Description

Technical Field

[0001] The invention relates to a preparation technology of a solar cell, in particular to an indoor photovoltaic cell with a simple sandwich structure, belonging to the technical field of solar energy. Background Art

[0002] In recent years, with the rapid development of Internet of Things technology, the number of terminal devices in its ecosystem has continued to grow exponentially, which has posed a challenge to the form of power source for the equipment. Therefore, the concept of indoor photovoltaics has gradually come into people's view. The biggest difference between indoor photovoltaics and conventional outdoor solar photovoltaic technology lies in the difference in incident light sources. Compared with the standard solar spectrum, the spectrum of indoor light sources is narrower and the intensity is weaker, and the optimal band gap of indoor photovoltaic application materials is around 1.9eV. Therefore, solar cells developed for traditional outdoor photovoltaic power generation are not necessarily suitable for indoor photovoltaic applications. Antimony sulfide has excellent material and optical properties, including simple binary composition, quasi-one-dimensional (Q1D) crystal structure, high absorption coefficient (10 4 -10 5 ), low melting point (~500°C) and high vapor pressure, which make it possible to prepare high-performance, flexible and lightweight antimony sulfide IoT power electronic devices, and thus have attracted widespread attention (Chem. Eng. J. 2022, 446 (4): 137400). The band gap of antimony sulfide is about 1.75 eV, which is close to the optimal band gap value for indoor photovoltaic applications, and is suitable for indoor photovoltaic applications and as a top cell light absorption material for silicon-based tandem photovoltaic cells (Adv. Funct. Mater. 2021, 31 (27): 2100265).

[0003] The preparation of high-quality absorption layer films is the key to obtaining high-efficiency indoor photovoltaic cell device performance. At present, the methods for preparing antimony sulfide films are mainly divided into two categories: vacuum method and solution method. FTO conductive substrates have been widely used in the research and preparation of photovoltaic devices, but whether it is a vacuum method or a solution method, it is extremely difficult to directly deposit and prepare high-quality antimony sulfide films on FTO conductive substrates. At present, the mainstream structure of antimony sulfide photovoltaic cells is FTO conductive substrate / electron transport layer / antimony sulfide absorption layer / hole transport layer / back electrode. Although the introduction of the electron transport layer can improve the deposition quality of the antimony sulfide film to a certain extent, the presence of the electron transport layer and the hole transport layer complicates the preparation process of antimony sulfide photovoltaic cells and increases the difficulty of preparing antimony sulfide photovoltaic cell devices. At the same time, the preparation process of the electron transport layer and the hole transport layer is usually accompanied by the use of toxic chemicals, which poses challenges to safety and environmental friendliness.

[0004] The near-space sublimation method is a thin film preparation method suitable for large-scale industrial production. It has the advantages of simple operation, independent evaporation source and evaporation substrate temperature, high deposition rate and easy large-area preparation. At present, it has been successfully used to prepare efficient commercial cadmium telluride thin film solar cells. The development of a process route suitable for directly depositing high-quality antimony sulfide thin films on conductive substrates is of great significance to promote the industrialization of antimony sulfide indoor photovoltaic cells. Summary of the invention

[0005] The present invention aims to solve the shortcomings of the above-mentioned prior art and provides a sandwich simple structure indoor photovoltaic cell and a preparation method thereof. The method of the present invention is based on the crystal nucleus engineering strategy, and directly prepares a high-quality antimony sulfide absorption layer film on a conductive substrate by a near-space sublimation method, and applies it to construct an indoor photovoltaic cell.

[0006] The present invention firstly discloses an indoor photovoltaic cell with a simple sandwich structure, whose device structure from bottom to top is FTO conductive substrate / antimony sulfide absorption layer / metal electrode, specifically, an antimony sulfide absorption layer is arranged on the FTO conductive substrate, and a metal electrode is arranged on the antimony sulfide absorption layer.

[0007] Furthermore, the thickness of the antimony sulfide absorption layer is 500-800 nm.

[0008] Furthermore, the thickness of the metal electrode is 60-120 nm, and the metal electrode is a gold electrode or a silver electrode.

[0009] The present invention also discloses a method for preparing the sandwich simple structure indoor photovoltaic cell, which specifically comprises the following steps:

[0010] Step 1: Cleaning of FTO conductive substrate

[0011] The FTO conductive substrate was ultrasonically cleaned in deionized water, acetone and anhydrous ethanol for 20-40 minutes respectively. After cleaning, it was blown dry with nitrogen and then placed in a UV ozone cleaning machine for cleaning for 20-40 minutes.

[0012] Step 2: Preparation of antimony sulfide absorber layer

[0013] The antimony sulfide absorption layer was prepared by the near-space sublimation method: the antimony sulfide powder was placed at the evaporation source of the near-space sublimation equipment, the FTO conductive substrate cleaned in step 1 was placed at the evaporation substrate of the near-space sublimation equipment, and the air pressure in the internal cavity of the equipment was reduced to 1 Pa by using a vacuum pump, and the evaporation substrate and the evaporation source were heated. The target temperature of the evaporation substrate was set to 100°C, the target temperature of the evaporation source was set to 300°C, the heating time was 2 minutes, and the heat preservation time was 15 minutes; the evaporation source was continued to be heated, the target temperature was set to 460-480°C, the heating time was 1 second, and the evaporation source was heated to 460-480°C. After reaching the set temperature, stop heating, cool the evaporation source temperature to 300°C for 5 minutes, and the seed layer preparation process is completed; heat the evaporation substrate and the evaporation source, the target temperature is 290-310°C, the heating time is 2 minutes, and the heat preservation is 15 minutes; keep the evaporation substrate temperature unchanged, continue to heat the evaporation source, the target temperature is set to 530-550°C, the heating time is 1 minute, and the heat preservation is 1-2 minutes, and the evaporation substrate and evaporation source are stopped from heating; turn off the vacuum pump, and after the equipment cavity returns to room temperature and normal pressure, take out the sample to obtain the antimony sulfide absorption layer;

[0014] Step 3: Preparation of metal electrodes

[0015] The metal electrode is prepared by thermal evaporation: the FTO conductive substrate / antimony sulfide absorption layer sample prepared in step 2 is placed in a thermal evaporation device, and the metal electrode is evaporated with an evaporation current of 100-130A, an evaporation voltage of 3-4V, and an evaporation time of 7-10min.

[0016] Furthermore, in step 1, the size of the FTO conductive substrate is cut according to the required size.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The present invention directly induces the preparation of high-quality antimony sulfide films on conductive glass substrates through a crystal nucleus engineering strategy.

[0019] (2) The FTO conductive substrate / antimony sulfide absorption layer / metal electrode sandwich simple structure indoor photovoltaic cell prepared by the present invention significantly simplifies the cell device structure and greatly shortens the device preparation cycle compared to the traditional conductive substrate / electron transport layer / antimony sulfide absorption layer / hole transport layer / metal electrode device structure.

[0020] (3) The present invention adopts a close-space sublimation method suitable for large-scale industrial production to prepare antimony sulfide thin films. This operation method has the advantages of being simple and easy to repeat, independent control of the evaporation source and the evaporation substrate temperature, high film deposition efficiency, and large-area preparation.

[0021] (4) The present invention uses antimony sulfide materials with high abundance, non-toxicity and excellent stability as the absorption layer, and the prepared environmentally friendly antimony sulfide indoor photovoltaic cell has an efficiency of 6.12%, showing broad application prospects in the field of indoor photovoltaics. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a sandwich simple structure indoor photovoltaic cell provided by the present invention, which comprises, from bottom to top, an FTO conductive substrate, an antimony sulfide absorption layer, and a gold back electrode.

[0023] Figure 2 This is a surface scanning electron microscope (SEM) photograph of the antimony sulfide film in the device with a seed layer according to Example 5 of the present invention.

[0024] Figure 3 This is a cross-sectional scanning electron microscope (SEM) photograph of the antimony sulfide film in the device with a seed layer according to Example 5 of the present invention.

[0025] Figure 4 This is an X-ray diffraction (XRD) spectrum of the antimony sulfide film in the device with a seed crystal layer in Example 5 of the present invention.

[0026] Figure 5 1 is an emission power spectrum diagram and integrated power of a WLED light source used in an indoor photovoltaic performance test of each embodiment of the present invention under an illumination of 1000 lux.

[0027] Figure 6 1 is a photocurrent density-voltage (JV) curve of the indoor photovoltaic cell with a seed crystal layer according to Example 5 of the present invention under 1000 lux WLED irradiation. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1: Optimization of the evaporation source temperature of the seed layer

[0030] Step 1: Cleaning of FTO conductive substrate

[0031] The FTO conductive substrate was ultrasonically cleaned in deionized water, acetone and anhydrous ethanol for 30 minutes respectively. After cleaning, it was blown dry with nitrogen and then placed in a UV ozone cleaner for cleaning for 30 minutes.

[0032] Step 2: Preparation of antimony sulfide absorber layer

[0033] Place the antimony sulfide powder at the evaporation source of the near-space sublimation equipment, place the FTO conductive substrate cleaned in step 1 at the evaporation substrate of the near-space sublimation equipment, use a vacuum pump to reduce the pressure of the internal cavity of the equipment to 1Pa, heat the evaporation substrate and the evaporation source, set the target temperature of the evaporation substrate to 100℃, set the target temperature of the evaporation source to 300℃, heat for 2min, and keep warm for 15min. Continue to heat the evaporation source, set the target temperature to 460-480℃, heat for 1s, stop heating after reaching the set temperature, cool the evaporation source temperature to 300℃ for 5min, and the seed layer preparation process is completed. Heat the evaporation substrate and evaporation source, the target temperature is 300℃, the heating time is 2min, and the heat is kept for 15min; keep the evaporation substrate temperature unchanged, continue to heat the evaporation source, set the target temperature to 540℃, heat for 1min, keep warm for 1.5min, and stop heating the evaporation substrate and evaporation source. Turn off the vacuum pump, wait until the equipment cavity returns to room temperature and normal pressure, take out the sample, and obtain the antimony sulfide absorption layer.

[0034] Step 3: Preparation of metal electrodes

[0035] The FTO conductive substrate / antimony sulfide absorption layer sample prepared in step 2 was placed in a thermal evaporation device to evaporate a metal electrode (Au electrode) with an evaporation current of 120A, an evaporation voltage of 3.5V, an evaporation time of 10min, and an electrode thickness of 100nm.

[0036] The target temperature of the evaporation source during the preparation of the seed layer was adjusted to produce different photovoltaic cells. The indoor photovoltaic performance of the device was then tested. The results are shown in Table 1.

[0037] Table 1. Indoor photovoltaic performance of photovoltaic cells prepared under different seed layer evaporation source temperature conditions

[0038]

[0039] It can be seen from Table 1 that the evaporation source temperature during the preparation of the seed layer has a great influence on the device performance. When the evaporation source temperature during the preparation of the seed layer is 470°C, the device efficiency is the highest.

[0040] Example 2: Optimization of the absorber layer evaporation substrate temperature

[0041] Step 1: Cleaning of FTO conductive substrate

[0042] The FTO conductive substrate was ultrasonically cleaned in deionized water, acetone and anhydrous ethanol for 30 minutes respectively. After cleaning, it was blown dry with nitrogen and then placed in a UV ozone cleaner for cleaning for 30 minutes.

[0043] Step 2: Preparation of antimony sulfide absorber layer

[0044] Place the antimony sulfide powder at the evaporation source of the near-space sublimation equipment, place the FTO conductive substrate cleaned in step 1 at the evaporation substrate of the near-space sublimation equipment, use a vacuum pump to reduce the pressure of the internal cavity of the equipment to 1Pa, heat the evaporation substrate and the evaporation source, set the target temperature of the evaporation substrate to 100℃, set the target temperature of the evaporation source to 300℃, heat for 2min, and keep warm for 15min. Continue to heat the evaporation source, set the target temperature to 470℃, heat for 1s, stop heating after reaching the set temperature, cool the evaporation source temperature to 300℃ for 5min, and the seed layer preparation process is completed. Heat the evaporation substrate and evaporation source, the target temperature is 290-310℃, the heating time is 2min, and the heat is kept for 15min; keep the evaporation substrate temperature unchanged, continue to heat the evaporation source, set the target temperature to 540℃, heat for 1min, keep warm for 1.5min, and stop heating the evaporation substrate and evaporation source. Turn off the vacuum pump, wait until the equipment cavity returns to room temperature and normal pressure, take out the sample, and obtain the antimony sulfide absorption layer.

[0045] Step 3: Preparation of metal electrodes

[0046] The FTO conductive substrate / antimony sulfide absorption layer sample prepared in step 2 was placed in a thermal evaporation device to evaporate a metal electrode (Au electrode) with an evaporation current of 120A, an evaporation voltage of 3.5V, and an evaporation time of 10min.

[0047] The target temperature of the evaporation substrate during the preparation of the antimony sulfide absorption layer was adjusted to produce different photovoltaic cells. The indoor photovoltaic performance of the device was then tested. The results are shown in Table 2.

[0048] Table 2. Indoor photovoltaic performance of photovoltaic cells prepared under different absorber layer evaporation substrate temperature conditions

[0049]

[0050] It can be seen from Table 2 that the absorption layer evaporation substrate temperature has a great influence on the device performance. When the evaporation substrate temperature is 300℃, the device efficiency is the highest.

[0051] Example 3: Optimization of the evaporation source temperature of the absorption layer

[0052] Step 1: Cleaning of FTO conductive substrate

[0053] The FTO conductive substrate was ultrasonically cleaned in deionized water, acetone and anhydrous ethanol for 30 minutes respectively. After cleaning, it was blown dry with nitrogen and then placed in a UV ozone cleaner for cleaning for 30 minutes.

[0054] Step 2: Preparation of antimony sulfide absorber layer

[0055] Place the antimony sulfide powder at the evaporation source of the near-space sublimation equipment, place the FTO conductive substrate cleaned in step 1 at the evaporation substrate of the near-space sublimation equipment, use a vacuum pump to reduce the pressure of the internal cavity of the equipment to 1Pa, heat the evaporation substrate and the evaporation source, set the target temperature of the evaporation substrate to 100℃, set the target temperature of the evaporation source to 300℃, heat for 2min, and keep warm for 15min. Continue to heat the evaporation source, set the target temperature to 470℃, heat for 1s, stop heating after reaching the set temperature, cool the evaporation source temperature to 300℃ for 5min, and the seed layer preparation process is completed. Heat the evaporation substrate and evaporation source, the target temperature is 300℃, the heating time is 2min, and the heat is kept for 15min; keep the evaporation substrate temperature unchanged, continue to heat the evaporation source, set the target temperature to 530-550℃, heat for 1min, keep warm for 1.5min, and stop heating the evaporation substrate and evaporation source. Turn off the vacuum pump, wait until the equipment cavity returns to room temperature and normal pressure, take out the sample, and obtain the antimony sulfide absorption layer.

[0056] Step 3: Preparation of metal electrodes

[0057] The FTO conductive substrate / antimony sulfide absorption layer sample prepared in step 2 was placed in a thermal evaporation device to evaporate a metal electrode (Au electrode) with an evaporation current of 120A, an evaporation voltage of 3.5V, and an evaporation time of 10min.

[0058] The target temperature of the evaporation source during the preparation of the antimony sulfide absorption layer was adjusted to produce different photovoltaic cells. The indoor photovoltaic performance of the device was then tested. The results are shown in Table 3.

[0059] Table 3. Indoor photovoltaic performance of photovoltaic cells prepared under different absorption layer evaporation source temperature conditions

[0060]

[0061]

[0062] It can be seen from Table 3 that the evaporation source temperature of the absorption layer has a great influence on the device performance. When the evaporation source temperature is 540℃, the device efficiency is the highest.

[0063] Example 4: Optimization of absorber layer deposition time

[0064] Step 1: Cleaning of FTO conductive substrate

[0065] The FTO conductive substrate was ultrasonically cleaned in deionized water, acetone and anhydrous ethanol for 30 minutes respectively. After cleaning, it was blown dry with nitrogen and then placed in a UV ozone cleaner for cleaning for 30 minutes.

[0066] Step 2: Preparation of antimony sulfide absorber layer

[0067] Place the antimony sulfide powder at the evaporation source of the near-space sublimation equipment, place the FTO conductive substrate cleaned in step 1 at the evaporation substrate of the near-space sublimation equipment, use a vacuum pump to reduce the pressure of the internal cavity of the equipment to 1Pa, heat the evaporation substrate and the evaporation source, set the target temperature of the evaporation substrate to 100℃, set the target temperature of the evaporation source to 300℃, heat for 2min, and keep warm for 15min. Continue to heat the evaporation source, set the target temperature to 470℃, heat for 1s, stop heating after reaching the set temperature, cool the evaporation source temperature to 300℃ for 5min, and the seed layer preparation process is completed. Heat the evaporation substrate and evaporation source, the target temperature is 300℃, the heating time is 2min, and the heat is kept for 15min; keep the evaporation substrate temperature unchanged, continue to heat the evaporation source, set the target temperature to 540℃, heat for 1min, keep warm for 1-2min, and stop heating the evaporation substrate and evaporation source. Turn off the vacuum pump, wait until the equipment cavity returns to room temperature and normal pressure, take out the sample, and obtain the antimony sulfide absorption layer.

[0068] Step 3: Preparation of metal electrodes

[0069] The conductive substrate / antimony sulfide absorption layer sample prepared in step 2 was placed in a thermal evaporation device to evaporate a metal electrode (Au electrode) with an evaporation current of 120A, an evaporation voltage of 3.5V, and an evaporation time of 10min.

[0070] By adjusting the deposition time during the preparation of the antimony sulfide absorption layer, different photovoltaic cells were prepared, and then the indoor photovoltaic performance of the device was tested. The results are shown in Table 4.

[0071] Table 4. Performance of indoor photovoltaic cells prepared under different absorption layer deposition conditions

[0072]

[0073] It can be seen from Table 4 that the deposition time of the absorption layer has a great influence on the device performance. When the deposition time is 1.5 min, the device efficiency is the highest.

[0074] Example 5: Performance comparison of devices without seed layer and with seed layer

[0075] Step 1: Cleaning of FTO conductive substrate

[0076] The FTO conductive substrate was ultrasonically cleaned in deionized water, acetone and anhydrous ethanol for 30 minutes respectively. After cleaning, it was blown dry with nitrogen and then placed in a UV ozone cleaner for cleaning for 30 minutes.

[0077] Step 2: Preparation of antimony sulfide absorber layer for seedless device

[0078] Place the antimony sulfide powder at the evaporation source of the near-space sublimation equipment, place the FTO conductive substrate cleaned in step 1 at the evaporation substrate of the near-space sublimation equipment, use a vacuum pump to reduce the pressure of the internal cavity of the equipment to 1Pa, heat the evaporation source and the evaporation substrate, set the target temperature to 300℃, heat for 2min, and keep warm for 15min. Keep the temperature of the evaporation substrate unchanged, continue to heat the evaporation source, set the target temperature to 540℃, heat for 1min, keep warm for 1.5min, and stop heating the evaporation substrate and evaporation source. Turn off the vacuum pump, wait until the equipment cavity returns to room temperature and normal pressure, take out the sample, and obtain the antimony sulfide absorption layer of the seedless layer device.

[0079] Step 3: Preparation of antimony sulfide absorption layer for devices with seed layer

[0080] Place the antimony sulfide powder at the evaporation source of the near-space sublimation equipment, place the FTO conductive substrate cleaned in step 1 at the evaporation substrate of the near-space sublimation equipment, use a vacuum pump to reduce the pressure of the internal cavity of the equipment to 1Pa, heat the evaporation substrate and the evaporation source, set the target temperature of the evaporation substrate to 100℃, set the target temperature of the evaporation source to 300℃, heat for 2min, and keep warm for 15min. Continue to heat the evaporation source, set the target temperature to 470℃, heat for 1s, stop heating after reaching the set temperature, cool the evaporation source temperature to 300℃ for 5min, and the seed layer preparation process is completed. Heat the evaporation substrate and the evaporation source, the target temperature is 300℃, the heating time is 2min, and the heat is kept for 15min. Keep the evaporation substrate temperature unchanged, continue to heat the evaporation source, set the target temperature to 540℃, heat for 1min, keep warm for 1.5min, and stop heating the evaporation substrate and the evaporation source. Turn off the vacuum pump, wait until the equipment cavity returns to room temperature and normal pressure, take out the sample, and obtain the antimony sulfide absorption layer of the seed layer device.

[0081] Step 4: Preparation of metal electrodes

[0082] The samples prepared in step 2 and step 3 were placed in a thermal evaporation device to evaporate a metal electrode (Au electrode) with an evaporation current of 120A, an evaporation voltage of 3.5V, and an evaporation time of 10min. The preparation of two antimony sulfide indoor photovoltaic cells was completed.

[0083] The indoor photovoltaic performance of devices with and without a seed layer was tested, and the results are shown in Table 5.

[0084] Table 5. Performance of indoor photovoltaic cells prepared with or without seed layer

[0085]

[0086] It can be seen from Table 5 that the indoor photovoltaic efficiency of the device with a seed layer is better than that of the device without a seed layer.

[0087] Figure 2 This is a surface scanning electron microscope (SEM) photograph of the antimony sulfide film in the device with a seed layer in this embodiment. It can be seen that the grain size is about 0.5 μm.

[0088] Figure 3 This is a cross-sectional scanning electron microscope (SEM) photograph of the antimony sulfide film in the device with a seed layer in this embodiment. It can be seen that the thickness of the absorption layer is about 600 nm.

[0089] Figure 4 This is an X-ray diffraction (XRD) spectrum of the antimony sulfide film in the device with a seed layer in this embodiment. It can be seen from the figure that the XRD diffraction peak corresponds to the antimony sulfide standard powder diffraction card, proving that the prepared antimony sulfide film is pure in phase and has good crystallinity.

[0090] Figure 5 The emission power spectrum and integrated power of the WLED light source used in the indoor photovoltaic performance test of each embodiment of the present invention under an illumination of 1000 lux are shown. The incident light power density of the WLED under an illumination of 1000 lux is 314 μW cm -2 .

[0091] Figure 6 This is the photocurrent density-voltage (JV) curve of the device with a seed layer in this embodiment under 1000 lux WLED irradiation, and the device efficiency is 6.12%.

[0092] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A simple sandwich structure indoor photovoltaic cell, characterized in that: The indoor photovoltaic cell is provided with an antimony sulfide absorption layer on a FTO conductive substrate, and a metal electrode is provided on the antimony sulfide absorption layer.

2. The sandwich simple structure indoor photovoltaic cell according to claim 1, characterized in that: The thickness of the antimony sulfide absorption layer is 500-800nm.

3. The sandwich simple structure indoor photovoltaic cell according to claim 1, characterized in that: The thickness of the metal electrode is 60-120 nm.

4. The sandwich simple structure indoor photovoltaic cell according to claim 1, characterized in that: The metal electrode is a gold electrode or a silver electrode.

5. A method for preparing a sandwich simple structure indoor photovoltaic cell according to any one of claims 1 to 4, characterized in that: After cleaning the FTO conductive substrate, an antimony sulfide absorption layer is prepared on the surface of the substrate conductive layer by a close-space sublimation method, and then a metal electrode is prepared on the antimony sulfide absorption layer by a thermal evaporation method.

6. The method for preparing a sandwich simple structure indoor photovoltaic cell according to claim 5, characterized in that: The specific steps include: Step 1: Cleaning of FTO conductive substrate The FTO conductive substrate was ultrasonically cleaned in deionized water, acetone and anhydrous ethanol for 20-40 minutes respectively, dried with nitrogen gas, and then cleaned in a UV ozone cleaning machine for 20-40 minutes; Step 2: Preparation of antimony sulfide absorber layer The antimony sulfide powder is placed at the evaporation source of the near-space sublimation equipment, and the FTO conductive substrate cleaned in step 1 is placed at the evaporation substrate of the near-space sublimation equipment. The air pressure in the cavity of the equipment is reduced to 1Pa by using a vacuum pump to evacuate air, and the evaporation substrate and the evaporation source are heated. The target temperature of the evaporation substrate is set to 100°C, and the target temperature of the evaporation source is set to 300°C. The heating time is 2min and the heat preservation time is 15min. The evaporation source is continued to be heated, and the target temperature is set to 460-480°C, and the heating time is 1s. After reaching the set temperature, the heating is stopped, and the evaporation source temperature is cooled to 300°C for 5min, and the seed layer preparation process is completed. The evaporation substrate and the evaporation source are heated, and the target temperature is 290-310°C, and the heating time is 2min, and the heat preservation time is 15min. Keeping the evaporation substrate temperature unchanged, continue to heat the evaporation source, and the target temperature is set to 530-550°C, and the heating time is 1min. The heat preservation time is 1-2min, and the heating of the evaporation substrate and the evaporation source is stopped; the vacuum pump is turned off, and after the equipment cavity returns to room temperature and normal pressure, the sample is taken out to obtain an antimony sulfide absorption layer; Step 3: Preparation of metal electrodes The FTO conductive substrate / antimony sulfide absorption layer sample prepared in step 2 is placed in a thermal evaporation device to evaporate a metal electrode with an evaporation current of 100-130A, an evaporation voltage of 3-4V, and an evaporation time of 7-10min.

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